This invention relates to organic nonlinear optical materials and, more particularly, to materials which exhibit a large second-order optical nonlinearity and good optical transmission.
Nonlinear optical materials appear to have potential applications in such emerging fields as optical communications, sensor protection and laser technology. Second-order nonlinear optical materials have been proposed for use in such devices as waveguides, frequency doublers, parametric amplifiers, electrooptic modulators and optical switches. However, organic materials having large optical nonlinearities which have so far been investigated have failed to satisfy all of the requirements demanded by these devices. A major detraction to most of the known organic second-order nonlinear optical materials is their color. The crystals of 2-methyl-4-nitroaniline (MNA), for example, are bright yellow. When working with diode lasers, the color of the nonlinear optical material must be considered and the lack of color in such material is the ideal. For an organic material to be of practical significance as a second harmonic generator, crystals of the compound must be phase matchable, i.e., capable of allowing the second harmonic signal to increase nonoptically as it passes through the crystal.